Afaik - block heaters were installed in other areas of an engine. There were always knockouts in NA engines for them. The coldest temps that I ever tried to start a car was in Timmins, Ontario at -40. My Subie (at the time) started but the gear shift wouldn't move for 10 minutes & the springs in the seats were frozen etc etc. I have also tried a light bulb near the battery to maintain some heat. I always took a parka, warm boots, gloves, toque, a sleeping bag & a candle for survival in the north in case of break down because the roads can get awful lonely in the winter.
I don't go that far north in the winter anymore . . .
Ian